A nut fastener assembly includes a nut assembly and a fastening clip. Opposite sides of the bottom of the nut assembly are provided with a pair of protrusions. The fastening clip includes a pair of lugs arranged on opposite ends of the fastening clip and extending towards the nut assembly, and a pair of receiving channels configured to respectively penetrate the pair of lugs. At least one of the pair of lugs is an adjustable lug including a blocking part and an elastic part. The distal end of the elastic part is movable relative to the distal end of the blocking part. The corresponding protrusion in the pair of protrusions can enter the corresponding receiving channel through a space between the distal end of the blocking part and the distal end of the elastic part to be held in the receiving channel.